Linear incendiary strand and method for prescribed fire ignition

ABSTRACT

An elongate, flexible, incendiary device for producing a nearly instantaneous source of flaming combustion along a linear pathway of indeterminate length. The incendiary device is provided in the form of a solid, continuous strand, such as, for example, a ribbon, tape, cord, filament, rope or tube. The device is comprised of means for rapid ignition along the longitudinal axis of the strand in co-linear arrangement with a solid or semi-solid combustible fuel composition. Upon ignition, the device produces flames from its exterior surface for a duration of time suitable for igniting nearby combustible matter. The incendiary device provides a nearly instantaneous line of fire for igniting prescribed fires, controlled burns, and backfires. A method for igniting vegetative matter over an area of land using one or more indeterminate lengths of a rapidly igniting linear incendiary strand.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority back to U.S. Application No.60/542,377, which was filed on 6 Feb. 2004.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention is based upon work supported by the Cooperative StateResearch, Education, and Extension Service, U.S. Department ofAgriculture, under Grant No. 2003-33610-13068. The federal governmenthas certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to incendiary devices and methods used toinitiate fires, more specifically, for the purpose of ignitingprescribed fires in forest and range land vegetation.

2. Description of the Related Art

Prescribed burning refers to the deliberate application of fire towildlands to achieve specific resource management objectives. Itinvolves the tasks of planning, igniting and controlling the fire. Knownfire behavior models are used to determine the range of weatherconditions that will permit accomplishment of sufficient fuel reductiongoals, while still allowing personnel to maintain control of the fire.Burning operations can only be conducted when fuel moistures are withina specified range, and weather conditions must be ideal in order toproduce a desirable level of fuels reduction with minimal risk of fireescape. Air quality is a significant concern, which may limit the timeframes available for conducting burn projects. Limited availablepersonnel and limited funding further hamper the ability of resourcemanagement personnel to meet their prescribed burning goals.

The two operational phases of prescribed burning are the ignition phaseand the holding phase. The holding phase involves controlling a firethat has been set, and this phase is highly dependent on theavailability of manpower and equipment. The present invention relates tothe ignition phase. Currently, there are two primary means of ignition:aerial ignition and ground ignition. Aerial ignition involves the use ofhelicopters to fly over the intended burn area and dispense eitherincendiary plastic spheres (as in U.S. Pat. No. 4,422,383) or a trail offlaming, gelled gasoline (as in U.S. Pat. No. 4,247,281). Helicopter useis very costly and requires a number of ground support personnel;however, it is the preferred method for treating large burn areas. Thereis a higher level of risk to personnel involved with aerial operations,and there is a limit to the level of precision that can be achieved withaerial ignition.

Handheld drip-torches, which have been used for decades, are thepredominate tool used for ground ignition. This method involvespersonnel walking across unburned fuels, in sequential strips throughthe burn unit, while dispensing a flaming diesel/gasoline mix. Dependingon vegetation conditions, this process can be extremely time-consumingor, alternatively, may require a significant number of ground personnel.Crew safety is also an obvious concern, as personnel are setting fire tomaterials through which they are walking. In short, the primary methodof igniting natural fuels, whether by aerial or ground means, is theapplication of flaming petroleum products to the natural fuels.

By contrast, the present invention involves an improved method for theignition of natural vegetative fuels that does not rely on theapplication of flaming petroleum products. Instead, the presentinvention is a filamentous incendiary material that will ignite rapidlyand sustain sufficient flaming combustion for the ignition of forestfuels.

The prior art includes a number of patents and published applicationsdirected toward various methods of igniting fires, but none of theseinventions possess the unique attributes of the present invention, whichare more fully described below. Much of the prior art relates to fuses,which are distinguishable from the present invention. A fuse is definedgenerally as a core of readily combustible material that is lighted atone end to carry a flame along its length to detonate an explosive atthe other end. Whereas a fuse works to transmit a signal (or flame)along its path from one point to another, the present invention isintended to ignite quickly (nearly instantaneously along its length) andsustain flaming combustion for a period of time sufficient to ignitewood, grass, straw, needles, moss, and any other type of fuel that is inclose proximity along the length of the strand of the present invention.

The prior art also includes deflagrating cords that igniteinstantaneously and provide a short-lived flash of heat sufficient toignite a rocket motor or vehicle air bag deployment charge. Unlike thepresent invention, these deflagrating cords do not provide the durationof flaming combustion necessary to light vegetative materials that mayhave a high moisture content. For this reason, the deflagrating cordsthat have been described in previous patent applications are not aseffective as the present invention in igniting forest vegetation.

There are several examples of the fuse-type ignition method. U.S.Publication No. 2002018941 (Smith, 2002) discloses a linear ignitionfuse with a shaped sheath that creates gas channels along the length ofthe fuse; U.S. Pat. No. 4,220,087 (Posson, 1980) describes a linearignition fuse with a gas channel that extends longitudinally; and U.S.Pat. No. 5,540,154 (Wilcox et al., 1996) provides a linear ignition fusewith an elongated core of non-detonating ignitive material, alongitudinally extending gas channel, a frangible sheath of inorganicmaterial surrounding the core and the channel, and a jacket of braidedfilaments encasing the sheath. U.S. Pat. No. 5,540,155 (Hill, 1996)relates to an elongate flexible fuse made of an oxidizing agent and afuel present in quantities that allow for a rate of burning of from 10seconds/meter to 250 seconds/meter.

There are also a number of patents that cover deflagrating cords. Someexamples are: U.S. Pat. No. 3,320,882 (Schulz, 1967), which discloses anigniter cord consisting of a high explosive compound and a particulatemetal enclosed in a metal sheath, for use in connection with propellantcharges and rocket ignition; U.S. Pat. No. 5,322,018 (Hadden et al.,1994), which describes a surface-initiating deflagrating materialconsisting of a pyrotechnic material and an inorganic binder, such assilica, carried on a carrier web preferably made of fiberglass and witha hollow core; and U.S. Pat. No. 3,367,266 (Griffith, 1968), whichrelates to a detonating and deflagrating fuse that has a wrapper offlexible material enclosing a cracked and discontinuous column of solidexplosive.

Several patents have attempted to deal with the specific problemsassociated with fire ignition for the purpose of agricultural practices,forest management, or amelioration of environmental contamination. U.S.Pat. No. 4,256,086 (Collett et al., 1981) covers a method for rapidlyigniting combustible material over a predetermined area of a field.Simply put, this method involves attaching combustible elements to aline and advancing the line across the field. U.S. Pat. No. 4,247,281(McGrew et al., 1981) describes a method of “slash burning” whereby ahelicopter carries a dispenser with a jelly-like mixture of aluma geland gasoline, and the mixture is ignited and dropped on the area to beburned. U.S. Pat. No. 5,429,494 (Kuehn, 1995) discloses a transportableignition device adapted for use in forestry management practices andconsisting of a fuel storage tank and a pressurizing assembly. The fuelis expelled from an application wand, ignited, and delivered to adistant target by virtue of the pressurized pump. U.S. Pat. No.4,422,383 (Couture et al., 1983) relates to a floating incendiary devicethat is dropped from an aircraft onto a combustible material on a bodyof water. The device includes an incendiary composition that issandwiched between a pair of discs that direct the resulting flameradially outwardly over the surface of the combustible material. Thelatter invention was intended to provide a method for dealing withhydrocarbon slicks that float on water and adversely affect the marineenvironment. U.S. Pat. No. 6,128,845 (Jacobson, 2000) relates to a firestarting flare for hand-held launchers that allows brush fires to bestarted remotely from the person controlling the device. The flareprojectile of the invention has a range of one hundred thirty yards andemits a shower of sparks over the immediate vicinity of where it lands.

The main object of the present invention is to provide a method ofigniting fires for the management of forest vegetation that is muchsafer for fire management personnel than the primary method currentlyemployed, which entails dispensing flaming petroleum while walkingthrough the area to be burned. A further object of the present inventionis to provide a method for fire ignition that is more effective inigniting forest vegetation than the fuse- or deflagrating cord-typemethods described above.

BRIEF SUMMARY OF THE INVENTION

Generally, the present invention provides an elongate, flexible,incendiary device for producing a nearly instantaneous source of flamingcombustion along a linear pathway of indeterminate length. the subjectincendiary device is provided in the form of a solid, continuous strand,such as, for example, a ribbon, tape, cord, filament, rope or tube. Thedevice is comprised of means for rapid ignition along the longitudinalaxis of the strand in co-linear arrangement with a solid or semi-solidcombustible fuel composition. Upon ignition, the device produces flamesfrom its exterior surface for a duration of time suitable for ignitingnearby combustible matter. The incendiary device of the presentinvention essentially provides a nearly instantaneous line of fire forigniting prescribed fires, controlled burns, and backfires.

The present invention's ability to generate the flaming combustionnecessary for igniting forest or agricultural vegetative fuels along alinear pathway, nearly instantaneously, distinguishes it from otherprior art devices. Present devices for providing rapid linear ignitioninclude linear ignition fuses, pyrotechnic quick match, and deflagrationcord. These devices provide an intense, momentary flame rapidly alongtheir lengths, but they do not provide the sustained flame generationrequired for igniting nearby woody materials.

The present invention further provides a method for igniting vegetativematter over an area of land using one or more indeterminate lengths of arapidly igniting linear incendiary strand. The strand(s) is/are placedupon the surface of the area of land to be burned, and then ignited in amanner that provides for the burning of the vegetative materialsaccording to desired fire behavior aspects. The present invention isparticularly well suited for the prescribed burning of forest andrangeland vegetation, and it is also suitable for use in the controlledburning of agricultural field residues.

In accordance with one aspect of the invention, the incendiary device isa solid elongate strand of indeterminate length possessing a degree offlexibility allowing it to be wound upon a spool for handheld deploymentacross an area of land.

In accordance with another aspect of the invention, the linearincendiary device is provided with weatherproofing features enabling thedevice to be deployed in the area to be burned days or weeks prior toignition.

In accordance with another aspect of the invention, the linearincendiary device may be ignited by direct flame contact, such as from amatch, or may be remotely initiated by electrical means.

In accordance with another aspect of the invention, the linearincendiary device is provided with means to cause the separation of thestrand into individually burning fragments shortly after ignition. Thisfeature is advantageous if the strand is draped over branches or otherdebris, and flame contact with surface fuels is desired to ensure acontiguous line of fire.

In accordance with another aspect of the invention, the linearincendiary device is comprised of materials derived from renewableresources, and provides a substitute for the petroleum-based productsnow used for igniting prescribed fires.

In accordance with yet another aspect of the invention, the method ofigniting fires using a linear incendiary strand provides improved meansto control and manipulate fire behavior, and also provides a greaterdegree of safety for burn personnel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary isometric view of a cord-like embodiment of alinear incendiary strand according to the present invention.

FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1.

FIG. 3 is a fragmentary isometric view of a tape-like embodiment of alinear incendiary strand according to the present invention. The severallayers of the tape are shown to be peeled upwardly away from the baselayer of the tape for illustrative purposes only.

FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3.

FIG. 5 is an isometric view of an area of land whereupon the linearincendiary strand of the present invention is shown to be placed forpurposes of illustrating a method of ignition according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a linear incendiary strand and a methodfor setting fire to vegetative matter over the surface of an area ofland. In general, the linear incendiary strand of the present inventionmay be embodied in a number of different strand-like physical forms,such as, for example, a tape, ribbon, cord, tube, or filament. Theselected shape of the device is not critical to fulfilling the centralobjects of the invention.

The strand is constructed of solid or semi-solid materials, and mustpossess a degree of physical flexibility to allow for it being woundupon a spool of suitable diameter for handheld deployment by a personwalking through an area to be burned. For example, the strand mayrequire sufficient bending flexibility to be radially wound about aspool with a core size of approximately three inches in diameter, andthe deployed strand should not tend to retain the circular shape of thespool upon which it was wound. Other means of strand deployment arecontemplated, such as by motorized vehicle or by helicopter; however,the requirement for flexibility is still important. The incendiarystrand may also be provided to users in the form of a loose coil in abox, bag, drum or other suitable container. The physical size of thestrand is selected to meet the same criteria for deployability, and atthe same time must allow for a sufficient quantity of componentmaterials to achieve desired burning qualities.

The linear incendiary strand of the present invention is furtherprovided with reinforcing means that provides a degree of longitudinaltensile strength to prevent separation while being pulled duringdeployment. Longitudinal reinforcing means may be provided by theinclusion of fibrous elements in the overall structure of the strand,such as an exterior sheath, a continuous textile substrate, or aselongate fiber particles in a structural composite matrix.

The strand may further be provided with means for fragmentation of thestrand subsequent to ignition, allowing the body of the strand to becomeseparated into individually burning segments. These segments, which maybe, for example, approximately six inches in length, will fall andprovide for the ignition of combustible materials at the ground surfaceif the strand is suspended by branches or other obstacles. Fragmentationmeans may be provided by the accelerated burning of longitudinalreinforcing elements at selectively spaced intervals along the strand.Alternatively, fragmentation may also be provided by the softening, ormelting, of certain structural elements of the strand, allowing thestrand to undergo physical transformation during burning from a solidstrand to indistinct globules of burning fuel, which may drip to groundand ignite surface fuels.

An important advantage of the incendiary device of the present inventionover prior art methods for igniting prescribed burns is the ability todeploy, or lay out, the subject linear incendiary strand throughout thearea to be burned prior to the commencement of burning operations. Theincendiary strand of the present invention is provided withweatherproofing features that enable the material to be exposed toambient weather conditions for an extended period of time before it isignited, without detrimental effects upon its performance.Weatherproofing features may include the incorporation ofwater-resistant coatings and compositions in the manufacture of thestrand; such coatings or compositions provide a water vapor barrier forother components of the strand that may be hygroscopic in nature.

The linear incendiary strand of the present invention incorporates arapid linear ignition means that provides for the high velocitypropagation of an ignition reaction along the longitudinal axis of thestrand. Such ignition reaction is characterized as a flame-producing,non-explosive deflagration, and does not exhibit the brisance or linearrate of burning that is characterized as a detonation. The rapidignition means is exemplified by an elongate pyrotechnic compositionthat, upon ignition, burns in a rapid manner producing hot gasses andincandescent particles capable of igniting the co-linearly arrangedcombustible fuel composition of the incendiary strand. Such rapidpropagation of an ignition reaction and subsequent ignition of the fuelcomposition provides a nearly instantaneous line of fire along the pathof the subject incendiary device. A self-sustaining, forward-movingflame front in vegetative fuels is developed gradually, from the instantof ignition until a steady state of burning is reached that exhibits arelatively constant rate of spread and intensity.

One means of providing rapid linear ignition along the incendiarystrand, although not exclusive of other alternatives, is theincorporation of a “piped fuse” in the structure of the strand. Thetechnology of piped fuses is known in the art of pyrotechnics, describedfor example in “Military and Civilian Pyrotechnics” (Ellern, 1968). Thepiped fuse, also known as “quick match” to those practiced in the art,is characterized as an elongate pyrotechnic element, such as a fuse,that is confined within the interior of an elongate close-fittingconduit. This conduit, normally serving the purpose of an exteriorsheath of the fuse assembly, provides a channel for gaseous combustionproducts and heat to be driven in a forward direction along the lengthof the fuse. The hot gasses and sparks pre-heat and ignite thepyrotechnic element in advance of the traveling wave of ignitionreaction, further accelerating the flame front to high linear velocityalong the longitudinal axis of the fuse assembly. The present inventionmay incorporate such a piped match structure in the construction of thestrand, whereby a pyrotechnic element is arranged centrally in a channeldefined by other structural elements of the strand. At least someproportion, preferably a major proportion, of the interior surface areaof the longitudinal gas channel of the strand is comprised of a solid orsemi-solid fuel component, which upon ignition will undergoself-sustained combustion and emit flames to the exterior surface of thestrand. The gas channel may further be formed by a suitable exteriorcovering, or sheath, such as, for example, paper, plastic film, orcoated fabric compositions.

The pyrotechnic element of the rapid linear ignition means of thepresent invention may be selected from a number of alternatives known inthe art. The element is provided in elongate form, and may be, forexample, an extruded strand formed from a mixture of an oxidizing agent,a fuel compound and an appropriate binder. A preferred pyrotechnicelement is comprised of a cellulose fiber substrate that is impregnatedand coated with a composition comprised of oxidizer and fuel compounds.The cellulose fiber substrate may be paper, or preferably, a loose wovencotton textile fabric. The pyrotechnic composition coated onto thecellulose fiber substrate is selected from chemical combinations knownin the art that provide a high heat of combustion, produce hot gasses,and eject incandescent particles (sparks) during thermal decomposition.Such pyrotechnic mixtures are typically used in display fireworks, andmay also function as solid rocket propellants. For example, a suitablemixture is comprised of ammonium perchlorate (30% by weight), potassiumperchlorate (30% by weight), powdered aluminum, 325 mesh (25% by weight)and binder (15% by weight).

As is known in the art, the pyrotechnic components may be mixed togetherwith a suitable binder that maintains the reactive chemicals in ahomogenous admixture, provides adhesion to the cellulose fibersubstrate, and provides a barrier to atmospheric or liquid water thatotherwise may cause degradation of reactive performance. The binder,which may also provide additional fuel for the ignition reaction, mustbe selected to provide the pyrotechnic composition with adequateflexibility when incorporated into the overall incendiary strandstructure. Suitable binders include, for example, plasticizedcellulosics such as cellulose nitrate and cellulose acetate,polyacrylate, elastomers such as poly-isoprene and poly-butadiene, andpolyolefins such as polyethylene and polypropylene. A preferred binderis cellulose acetate butyrate, which provides exceptional waterresistance and is derived from renewable resources.

The cellulose fiber substrate is coated with the pyrotechnic compositionusing techniques commonly known in the art of fabric and paper coating.Examples of such techniques are roll coating, immersion coating, andspray coating. The coated cellulose fiber substrate, which may beprovided as a wide or narrow web in a continuous, indeterminate length,may then be slit into narrower widths of suitable dimension formanufacture of the incendiary strand.

A solid or semi-solid fuel component comprises a major proportion, byweight, of the body of the present incendiary strand. The fuel componentis selected from known combustible substances, or mixtures ofsubstances, that undergo self-sustained combustion in a manner in whichflames are produced of suitable length and intensity to cause theignition of nearby vegetative fuels. Further, the amount of fuelcomponent, as distributed along the length of the strand, must besufficient to sustain burning at any point along the strand for a periodof time sufficient to raise the temperature of nearby vegetative matterto the point of ignition. Some dead woody fuels may possess a relativelyhigh degree of bound cellular moisture, requiring a certain intensityand duration of incident heat energy before the water is driven off to apoint where burning of the vegetative matter can ensue in aself-sustained process. The incendiary strand of the present inventionis provided with a fuel component that exhibits flaming combustion for aduration of from ten seconds to five minutes in time, as measured at anypoint along the length of the strand.

Suitable solid or semi-solid combustible substances for the fuelcomponent are widely known in the art of fire-starting devices. Ingeneral, a composition is selected that is capable of being formed intoa strand, such as by extrusion, coating onto a substrate carrier, or byencasement of a granular form of the composition in a suitable sheath.As described earlier, the fuel composition must possess a sufficientdegree of flexibility, and must not fracture as the strand is twistedand bent. Possible alternatives for the fuel component include waxes,tars, natural resins, latex rubbers, gelled hydrocarbons, polyethylene,polypropylene, poly-isoprene, poly-butadiene, and silicon rubber.Certain cellulose fibers such as sawdust, wood pulp, cotton linters andground vegetative matter may be incorporated into the selected fuelcomposition to act as a filler and to provide structural reinforcement,additional fuel, and resiliency. Since it is an objective of the presentinvention to replace the petroleum based products now used in controlledburning operations, it is desired to select a fuel component that isderived from renewable resources. A preferred fuel component is acomposition based on resinous products from conifer trees. Inparticular, the higher boiling point fractions of conifer extractivesprovide suitable caloric heat output during combustion, and possess adegree of thermoplasticity that is advantageous for production of anincendiary strand as contemplated in the present invention. The conifertree resins may be obtained commercially from, for example, pine stumpdistillation or extraction, collection of live tree exudates, or talloil produced by the pulp and papermaking processes. A furtherdescription of the preferred resin-based fuel composition and theprocess used to produce it is provided in the examples below.

The present invention includes a method of igniting vegetative matterover an area of land using a solid, flexible, elongate incendiary strandas described above. In general, the vegetative matter referred to hereinmay be defined as combustible plant material desirous of being consumedby burning, and may include logging slash, down and dead woodymaterials, leaves, conifer needles, brush, grasses, weeds, andagricultural residues. The present invention is particularly well suitedfor use in prescribed burning activities on forested lands to accomplishnatural fuels reduction, wildlife habitat improvement, and logging slashdisposal. In addition to the above listed land management applications,the incendiary strand may also provide an improved means for ignitingbackfires and burnouts during wildfire control operations.

A significant improvement of the present invention over previous methodsof igniting controlled fires is the ability provided to deploy the meansof ignition before actual burning operations commence, thereby reducingthe number of personnel required during the burn. The linear incendiarystrand may be deployed, or laid out, in predetermined patternsthroughout the area to be burned in accordance with known practices toachieve desired fire behavior. When a “Strip-Head” firing pattern (asshown in FIG. 5) is desired, the incendiary strand will be placed alongnearly parallel pathways across the area to be burned in such a manneras to provide a desired level of fire intensity and rate of spread.Alternatively, a circular ignition pattern may be selected forconducting a “mass ignition” of a large area, wherein the strand wouldbe placed in concentric circles of incrementally increasing diameter.The distance between adjacent pathways, or strips, is determined in partby the amount and type of combustible materials, the slope of the area,and the favorable wind direction for the safe conduct of the burn.

The incendiary strand may be deployed by personnel walking along theintended ignition strips, or may similarly be deployed by vehicular oraerial means. The incendiary device may be provided as a continuousstrand of indeterminate length wound upon a spool of appropriate sizefor the means of deployment. For manual application, a spool size thatwould allow for a person to walk over difficult terrain with a rotaryunspooling apparatus is desired. A larger sized spool may be appropriatefor vehicular or aerial deployment, and may require powered unspooling.

Each of the several individual lengths of incendiary strand are ignitedin succession, at intervals of time selected to achieve desired firebehavior characteristics. The strands may be ignited by the directapplication of flame to an exposed surface of the pyrotechnic element ofthe strand. The strand may be ignited at a cut end, or at any locationalong the strand where a portion of the pyrotechnic element has beenexposed by removal of outer materials. A distinct advantage of thepresent invention is the ability to alternatively initiate strandcombustion by electrical means, using, for example, squibs or what areknown as “electric matches” in the pyrotechnics field. Electric matchesare often used to ignite lifting charges for aerial fireworks, and theyoperate by the electrical resistance heating of a wire element, whichcauses a surrounding bead of pyrogenic compound to ignite. An electricmatch may be inserted into an opening of the subject incendiary strandand will cause the strand to ignite upon electrical activation. Theelectrical apparatus selected for such initiation of the strand is not asubject of the present invention, as a number of suitable ignitionsystems are known in the art of blasting or pyrotechnics. Remoteelectrical ignition of the incendiary strand provides a higher degree ofsafety for personnel conducting controlled burns, and it also affords ameans to ignite successive burn strips rapidly when a sustained highintensity fire is desired.

The improved ignition method of the present invention may also besuitably employed in the setting of backfires, or burn-outs, in wildfirecontrol activities. A linear incendiary strand, as described, may beplaced among combustible vegetative matter adjacent to fire controllines in the path of an advancing wildfire. The fire control lines may,for example, be for the purpose of protecting houses, groups of houses,or resources of special concern from destruction by the wildfire.Additional ignition strands may also be placed along strips parallel inorientation to the first strip, at a distance of spacing between stripsdetermined accordingly for fuel, weather and topographical conditions.The individual incendiary strands may then be ignited in anappropriately timed sequence whereby a line of fire is drawn from thecontrol line outwardly towards the advancing wildfire, and against thedirection of the prevailing winds. Through the use ofradio-signal-activated, electrical ignition apparatus, personnel may beafforded the ability to conduct such an operation remotely and from asafe distance from the fire's path. The effectiveness of theabove-described method is further enhanced when the incendiary strandsare ignited precisely at the onset of indraft winds generated from theadvancing wildfire.

EXAMPLE NO. 1

Referring now to FIG. 1 and FIG. 2, a specific embodiment of the presentinvention is shown as having the physical form of an elongate cord-likestructure of indeterminate length. FIG. 1 illustrates a fragmentaryisometric view of a linear incendiary strand; FIG. 2 shows across-sectional view of the same strand taken along line 2-2 of FIG. 1.The incendiary strand 10 a has a tubular body formed of a resinous fuelcomposition 11; the outside diameter of such strand is preferably about¾ inch (1.9 cm). The central longitudinal duct of strand 10 a forms agas channel 13, having an inside diameter of about ¼ inch (0.64 cm).Pyrotechnic element 17, comprised of fabric substrate 12 with a coatingof pyrotechnic composition 16, is disposed centrally within gas channel13, with its lateral edges fixedly embedded in fuel composition 11 alongthe longitudinal axis of strand 10 a. A plurality of vent passages 14are radially disposed about the circumference of strand 10 a to form agrouping; such vent passage groupings are arranged at equidistantintervals along the strand. Outer waterproofing layer 15 covers theexterior surface of strand 10 a, including the outer opening of the ventpassages 14.

Pyrotechnic element 17 is produced by first soaking fabric substrate 12in a saturated aqueous solution of a water-soluble oxidizing agent,preferably ammonium perchlorate or potassium nitrate. A preferred fabricis bleached cotton cheesecloth that has a denier of around 60 threadsper inch, and is supplied in rolls of about 16 inches wide. Thismaterial is highly absorbent, has relatively strong tensile strength,and has open interstitial voids, which may be filled with a pyrotechniccomposition during the coating process. The fabric is then squeezed outto remove excess solution and dried in a warm air drying tunnel, leavingthe cotton threads of the fabric impregnated with oxidizing agent.

The impregnated cotton fabric is coated with a rapidly burningpyrotechnic composition 16 using processes typically used in the fabriccoating trade, such as, for example, a process utilizing an immersioncoating line. The pyrotechnic composition is comprised of ammoniumperchlorate (30% by weight), potassium perchlorate (30% by weight),powdered aluminum, 325 mesh (25% by weight) and a liquid binder (15% byweight). A suitable binder is prepared by dissolving nitrocellulosesolids (12% nitrogen content) in acetone, in proportions to achieve aviscous heavy-bodied solution. The coated fabric is dried, and thenrotary slit into strips approximately ½ inch (1.27 cm) in width andrewound onto suitable spools.

The fuel composition 11 is comprised of a combustible thermoplasticresin in homogenous admixture with cellulose fiber particles that havebeen impregnated with an oxidizing agent. The thermoplastic resin ispreferably a mixture of a pine resin derivative (80% by weight),cellulose acetate butyrate (15% by weight), and a plasticizing agent (5%by weight). A suitable pine resin derivative that is commerciallyavailable is VINSOL resin, manufactured by Hercules Inc., which isproduced from the steam distillation of pinewood stumps. A suitableplasticizing agent is selected from the group of plasticizers that arecompatible with cellulosic and rosin-based products, and provides theincendiary strand with adequate flexibility. A preferred,vegetable-based plasticizer is glyceryl triacetate, availablecommercially as TRIACETIN, from Eastman Chemical Company. Other suitableplasticizers include triethyl citrate (CITROFLEX 2, from Morflex, Inc.)and butyl ricinoleate (FLEXRICIN P-3, from CasChem, Inc.). Theingredients are mixed together at a temperature of about 200 degrees C.to form a homogenous thermoplastic composition.

A cellulose fiber filler material is selected to provide reinforcingstrength to the incendiary strand and to provide additional fuel forcombustion. A preferred fibrous material is finely divided sawdust.Specifically, sawdust derived from the western red cedar tree is easilypulverized into individual fibers having a large length-to-width ratio.Further, this fibrous filler material derived from cedar wood or bark islight in weight, provides a high heat of combustion, and readily absorbscertain liquids.

The cedar fibers are first soaked in a saturated aqueous solution of awater-soluble oxidizing agent, such as potassium nitrate or ammoniumperchlorate, and then dried, in order to provide additional oxygen forcombustion of the incendiary strand. This oxidizer-enhanced cedar fiberis then added to the hot resin composition in proportions to achieve athermoplastic composite having a thick, dough-like consistency at aprocessing temperature of around 150 degrees C. Care must be exercisedto ensure that the processing temperature of the composition does notapproach the decomposition temperature of the oxidizing agent used.

The fuel composition 11 is formed into the shape of a hollow tube,having embedded within a portion of its interior walls the pyrotechnicelement, using a cross-head extrusion technique. This extrusion processis similar to that used in the plastics industry to form thermoplasticlayers over elongate strands, such as in the application of plasticinsulation to electrical wires. The incendiary strand 10 a is formed byfeeding pyrotechnic element 17 through a slotted aperture centrallydisposed within a specifically designed extrusion head, while fuelcomposition 11 is forced under pressure through the head. In thismanner, a continuous strand is formed, and the strand is then cooled tosolidify the thermoplastic composition. The extrusion apparatus may be asingle or double screw extruder, and it is set up in a manner in whichexternal heat is provided to melt the thermoplastic material instead ofusing adiabatic heating through high pressure compression.

The cooled incendiary strand is then subjected to a perforating ordrilling operation whereby vent passages 14 are produced around thecircumference of the strand, at incremental distances of about 6 inches(15.2 cm) along its longitudinal axis. Outer waterproofing layer 15 maybe applied by passing the strand quickly through an immersion bath of amelted thermoplastic polymer, such as plasticized cellulose acetatebutyrate, and rapidly cooled using a coolant bath. Alternatively, outerwaterproofing layer 15 may be applied by the spiral wrapping of anadhesive-backed cellulose acetate film about the strand's outer surface.

The incendiary strand 10 a is ignited by the application of flame topyrotechnic element 17. The ignition reaction consumes pyrotechniccomposition 16 at a relatively slow linear rate initially, discharging ahigh proportion of gaseous products of combustion away from the strand.As hot gasses are forced into gas channel 13, the ignition reactionaccelerates to a high velocity of propagation along the surface ofpyrotechnic element 17 due to the projection of heat forward along thegas channel 13. The ignition reaction further initiates combustion offuel composition 11 along the internal surface of gas channel 13, whichburns readily due to the incorporation of the oxygen-providing agent inthe fibrous filler. The heat of combustion produces elevated internalstrand pressure sufficient to burst outer waterproofing layer 15 at theouter terminus of the vent passages 14, allowing flames and sparks toemit therefrom. As the strand burns internally, the heat generatedsoftens and melts fuel composition 11, most noticeably in the area ofthe vent passages 14. The strand's structural integrity fails first atthese locations, causing the strand to separate into individuallyburning pieces, which may then fall to the ground if they happen to beelevated. The strand, or the pieces of the strand, continue(s) to burnafter transitioning into an amorphous melt, for a period of up to fiveminutes and with flame lengths of about 4 inches (10.2 cm).

EXAMPLE NO. 2

In an alternative embodiment, the incendiary device of the presentinvention is shown in FIG. 3 and FIG. 4 as having the physical form of awide tape, or ribbon, of indeterminate length. FIG. 3 illustrates afragmentary isometric view of a linear incendiary strand 10 b of suchstructure, herein referred to as an incendiary tape; FIG. 4 shows across-sectional view of the same strand, taken along line 4-4 of FIG. 3.The incendiary tape 10 b is produced as a lamination of multiple layers,comprising upper covering layer 22, lower covering layer 21, fuelcomposition 24 and pyrotechnic element 23. Fuel composition 24 ispresent in a discontinuous pattern on both upper and lower surfaces ofpyrotechnic element 23, forming central longitudinal gas channel 26 inconnective arrangement with multiple lateral gas channels 25. Lateralgas channels 25 are open to the exterior lateral edges of tape 10 b, andare longitudinally offset to either side of longitudinal gas channel 26.

Pyrotechnic element 23 is produced using the same materials and in thesame manner as described for pyrotechnic element 17 of the previousexample. The only difference between the two examples is the width towhich pyrotechnic element 23 of the present example is to be slit, whichis about 5 inches (12.7 cm).

Fuel composition 24 is produced using the same combustible resincomposition as described for fuel composition 11 of the previousexample; however, the cellulose fiber filler material is excluded fromthe present example.

Upper covering layer 22 and lower covering layer 21 provide a waterbarrier and protective covering for fuel composition 24 and pyrotechnicelement 23. In addition, the inner surfaces of covering layers 22 and 21provide envelopment for channeling hot gasses produced by combustion ofpyrotechnic element 23, specifically along longitudinal gas channel 26and lateral gas channels 25. The material selected for upper and lowercovering layers 22, 21 may be polymeric film, coated fabric, or paper. Apreferred material is 30 lb. creped kraft paper, which provides suitableflexibility for winding the incendiary tape 10 b radially about a spoolcore. Creping allows the outer surface to stretch slightly, and theinner surface to compress slightly without damaging the functionalintegrity of the covering.

The creped kraft paper is impregnated with an oxidizing agent to enhanceits burning characteristics. In a process similar to that used forimpregnating fabric substrate 12 of pyrotechnic element 17, the paper isfirst soaked in a saturated aqueous solution of an oxidizing agent suchas ammonium perchlorate or potassium nitrate, and then dried.Preferably, this oxidizing agent treatment is performed concurrentlywith the wet creping process used to produce the creped paper. The driedpaper is subsequently impregnated and coated with a waterproofing agentthrough an immersion and drying process known in the papermakingindustry to produce coated paper. The waterproofing agent is preferablya cellulose acetate butyrate lacquer; however, microcrystalline waxsolutions are also suitable provided they are non-petroleum based. Thecreped kraft paper, treated as described, is slit to 5 inch (12.7 cm)widths and wound upon spools.

The separate layers of incendiary tape 10 b are combined together toform a permanent lamination in a process typically utilized in the tapeconverting trade. Spools of upper covering layer 22 and lower coveringlayer 21 are mounted on separate feed spindles of a roll laminatingapparatus. A spool of pyrotechnic element 23 is similarly mounted on afeed spindle between the spools of upper and lower covering layers.Pyrotechnic element 23 is drawn through a double-sided slot-dieextrusion apparatus comprising two separate slot die extrusion heads oneach side of the pyrotechnic element. The individual extrusion heads areprovided with electrical or pneumatically operated shut-off valves, andthe heads are arranged to apply two separated strips of the heatedthermoplastic fuel composition 24 to each side of pyrotechnic element23. Coating thickness is about 20 mils (0.020 inch) per side. The flowfrom each extrusion head is modulated by linear indexing means toprovide discontinuous strips longitudinally. The resultant areas ofpyrotechnic element 23, devoid of fuel composition 24 on both sides,form lateral gas channels 25.

Upper and lower covering layers 21, 22 are drawn together with thecoated pyrotechnic element 23 and fed through suitably spaced pressurerollers to form a permanent lamination having a total thickness of about0.060 inch (60 mils). Fuel composition 24 has superior adhesivequalities and is similar in form to commercially available hot meltglues. As such, the thermoplastic fuel composition 24 is heated anddriven under pressure to the heated extrusion heads in a similar fashionas other hot melt coatings.

In operation, incendiary tape 10 b is ignited by direct flame contactwith pyrotechnic element 23, the combustion of which is similar to thatdescribed in the previous example. The ignition reaction propagatesrapidly along longitudinal gas channel 26, and subsequently along eachlateral gas channel 25, which results in a discharge of flames andsparks from points along the edges of the tape. In a very short timeafter ignition, the heat generated by the combustion of pyrotechniccomposition 16 is sufficient to burn through upper and lower coveringlayers 21, 22, as well as fabric substrate 12, causing the tape 10 b toseparate into individually burning pieces. Although pyrotechniccomposition 16 is present throughout the entire pyrotechnic element 23,it does not burn rapidly where it is sandwiched between layers of fuelcomposition 24.

The manufacturing process described is based upon producing a singlecontinuous strand 5 inches (12.7 cm) wide and of a length limited bypractical roll lengths of the component materials. A wide web processmay also be utilized to produce the incendiary tape, whereby wide widthmaterials and machinery are used to produce a master roll, which is thenslit into multiple rolls of tape having a width of about 5 inches (12.7cm) each. Such a process may afford much greater efficiencies ofproduction.

EXAMPLE NO. 3

The ignition method of the present invention is suitably adapted for usein conducting a type of controlled burn that is known in the art as HighEnergy or Mass Ignition burning. This type of burning may be used tomitigate air pollution concerns by creating a fire of high enoughintensity to generate strong convective transport of smoke vertically,resulting in the dilution and dispersion of particulate emissions from afire. (Ottmar et. al., 2001). In addition, it may also be desirable togenerate sufficient heat energy over the fire to enable the smoke columnto reach the lifting condensation level of the atmosphere, where cloudscavenging of smoke may substantially reduce particulate levels (Radkeet al., 1991). A fire-generated convection column that has a greatermeasure of vertical kinetic energy than that presented horizontally byatmospheric winds will tend to rise directly upward for a distance abovethe fire, allowing gasses and embers to cool. A weak smoke column willbe tilted over by ambient winds, or may adhere to the hillside directlyover a burn area, often leading to fire escape across established firelines by the transport of hot gasses and sparks. High energy burning hasbeen practiced in the past most effectively using aerial ignitionmethods, as rapid ignition and a sustained rate of fire spread isrequired to maintain sufficient fire intensity (McCrea, 1996).

Referring now to FIG. 5, a method of igniting vegetative matteraccording to the present invention will be described with reference toits use on an area of forested land that has been logged, generallydesignated at 30. The area of land to be burned 31 is defined by outerboundaries 32, and has upon its ground surface forest litter, naturallyoccurring surface vegetation, and logging slash 33, which shall hereinbe referred to in the aggregate as “fuels.” For the purposes of thisexample, it is assumed that there exists in area 31 approximately 2.5 kgof dead and dry fuels 33 available for burning per square meter ofsurface area. The wind direction is indicated by arrow 34, and isassumed to have a velocity of six meters per second. Multiple separatelengths of a solid, flexible incendiary strand, as described earlier,are representatively shown along intended burn strips (35 a, 35 b, 35c); in this example, the strips are spaced approximately 20 metersapart.

As is common practice in the art, fire is first set to fuels lyingadjacent to the downwind boundary 32 a, and a backing fire is allowed toburn slowly into the direction from which the wind is blowing. Thisbacking fire is not shown in the present drawing for purposes ofillustrative clarity; however, its purpose is to consume fuels near theboundary to help prevent unwanted downwind fire spread across controllines. During this period of relatively low intensity burning, smokecolumn 37 is generally tilted over by the ambient wind, transportingsmoke and ash particles directly across downwind boundary 32 a. Thelinear incendiary strand lying along the first interior burn strip 35 ais ignited as soon as the backing fire has spread a sufficient distanceaway from the downwind boundary 32 a to provide a reasonably safe bufferstrip devoid of unburned fuels. The strand may be ignited, for example,by direct flame contact from friction matches, a handheld lighter, atorch, or by remote electrical means. The incendiary strand ignitesnearly instantaneously along its entire length, and flames emitting fromthe strand subsequently ignite adjacent fuels 33. The resulting line offire spreads through unburned fuel in the direction of the wind,creating indrafts that draw the backing fire toward it. The interactionof the two parallel lines of fire may generate a significant level offire intensity between them, resulting in an increase in convectiveenergy over the fire. In accordance with known fire behavior principles,the previously tilted smoke column 37 will tend to rise to a verticalorientation when the (kinetic) power of the fire is greater than the(kinetic) power of the wind (Nelson, 2003), a criteria which isdependent upon fire intensity and wind speed. For the given amount offuels and given wind velocity assumed in this example, a sustained firerate of spread greater than 0.08 meters per second (16 feet per minute)is necessary to develop and maintain a strong vertical smoke column(Radke et. al., 1991). In practice, rate of spread requirements willvary depending on actual fuel characteristics such as moisture content,arrangement, and particle size, as well as weather factors such astemperature and humidity.

The second strip, and each successive strip thereafter, is caused to beignited at intervals of approximately five minutes each, based on the20-meter spacing between strips and the desired 0.08 meters per secondrate of spread. The rapid ignition characteristics provided by thepresent incendiary strand support this accelerated rate of burning, arate which is needed in order to maintain the desired level of fireintensity and resultant smoke column strength. If this level of burningis allowed to decrease, the ambient wind 34 may force the smoke column37 to tilt over toward the downwind boundary 32 a. The tilted column mayresult in undesirable low-level smoke transport to sensitive downwindareas and the possibility of an escaped fire due to hot embers fallingout of the column onto unburned forest fuels. This process of stripignition is continued progressively along the length of the area to beburned, until all fuels have been consumed.

The present invention has a number of important features and advantages.It provides a means to initiate a nearly instantaneous line of fire incombustible materials over a ground surface, allowing for a greaterability to manipulate and control fire behavior. Ignition of prescribedfires using the present incendiary strand does not require personnel tobe located in hazardous areas of unburned fuels with fire nearby, as isnow the case when fires are ignited using handheld drip torches. Burningoperations may be conducted under conditions which may otherwiserestrict the use of fire, due to smoke dispersal problems or high fuelmoisture. More effective backfiring operations may be conducted to limitthe spread of destructive wildfires, by igniting backfires at the onsetof an approaching fire's indraft without putting personnel at risk. Thepresent invention also offers an alternative to petroleum-based ignitionmethods by utilizing materials obtained from renewable resources.

Although only certain preferred embodiments of the present inventionhave been shown and described, it will be apparent to those skilled inthe art that many changes and modifications may be made withoutdeparting from the invention in its broader aspects. The appended claimsare therefore intended to cover all such changes and modifications asfall within the true spirit and scope of the invention.

Definitions

The term “adiabatic” means of, relating to, or being a reversiblethermodynamic process that occurs without gain or loss of heat andwithout a change in entropy.

The term “brisance” means the shattering effect of the sudden release ofenergy in an explosion.

The term “deflagrate” means to burn or cause to burn with great heat andintense light.

The term “hygroscopic” means readily absorbing moisture, as from theatmosphere.

The phrase “nearly instantaneous” is used to describe a rapid rate offlame propagation along a linear pathway for the purpose of initiatingfires in vegetative fuels. An ignition propagation rate of 100 metersper second along the subject incendiary strand is considered nearlyinstantaneous for the purposes of the present invention.

The term “squib” refers to a small tube or block that contains a smallquantity of ignition compound in contact with a wire bridge heatingelement.

REFERENCES

Ellern, H., 1968. Military and Civilian Pyrotechnics. ChemicalPublishing Co. Inc., New York, N.Y.

McRae, D. J. 1996. Prescribed Fire Aerial Ignition Strategies. NorthernOntario Development Agreement; Technical Report TR-33.

Ottmar, R. D., J. L. Peterson, B. Leenhouts and J. E. Core. 2001. SmokeManagement Techniques to Reduce or Redistribute Emissions, p. 141-162 inSmoke Management Guide for Prescribed and Wildland Fire, 2001 Edition.National Wildfire Coordinating Group, pub. #NFES-1279.

Nelson, R. M., Jr. 2003. Power of the Fire—A Thermodynamic Analysis.International Journal of Wildland Fire, 12, 51-65.

Radke, L. F., and D. E. Ward. 1991. Prescriptions for Biomass Fire SmokeReductions in Proceedings, 11th Conference on Fire and ForestMeteorology; April 16-19, 1991; Missoula, Mont.: 460-469.

1. A linear incendiary strand comprising: a solid or semi-solid fuelcomponent; rapid linear ignition means; and reinforcing means.
 2. Thelinear incendiary strand of claim 1, wherein the fuel component isselected from the group consisting of waxes, tars, natural resins, latexrubbers, gelled hydrocarbons, polyethylene, polypropylene,poly-isoprene, poly-butadiene, and silicon rubber.
 3. The linearincendiary strand of claim 2, wherein the fuel component furthercomprises a filler.
 4. The linear incendiary strand of claim 3, whereinthe filler comprises cellulose fibers.
 5. The linear incendiary strandof claim 4, wherein the filler is selected from the group consisting ofsawdust, wood pulp, cotton linters, and ground vegetative matter.
 6. Thelinear incendiary strand of claim 3, wherein the filler is sawdustfibers derived from the western red cedar tree.
 7. The linear incendiarystrand of claim 1, wherein the fuel component is a compositioncomprising conifer tree resins.
 8. The linear incendiary strand of claim1, wherein the fuel component is comprised of a combustiblethermoplastic resin in homogenous admixture with cellulose fiberparticles that have been impregnated with an oxidizing agent.
 9. Thelinear incendiary strand of claim 8, wherein the thermoplastic resin isa mixture of a pine resin derivative, cellulose acetate butyrate, and aplasticizing agent.
 10. The linear incendiary strand of claim 9, whereinthe plasticizing agent is selected from the group consisting of glyceryltriacetate, butyl ricinoleate and triethyl citrate.
 11. The linearincendiary strand of claim 1, wherein the fuel component sustainsburning at any point along the strand for a period of time sufficient toraise the temperature of nearby vegetative matter to the point ofignition.
 12. The linear incendiary strand of claim 1, wherein the fuelcomponent exhibits flaming combustion for a duration of from ten secondsto five minutes, as measured at any point along the length of thestrand.
 13. The linear incendiary strand of claim 1, wherein the rapidlinear ignition means comprises an elongate pyrotechnic element.
 14. Thelinear incendiary strand of claim 13, wherein the elongate pyrotechnicelement is confined within the interior of an elongate close-fittingconduit.
 15. The linear incendiary strand of claim 13, wherein theelongate pyrotechnic element is arranged centrally in a channel definedby other structural elements of the strand.
 16. The linear incendiarystrand of claim 13, wherein the fuel component comprises one or moreplaniform layer(s) of combustible thermoplastic resin, and wherein thefuel component and elongate pyrotechnic element are laminated between anupper covering layer and a lower covering layer to form a tape.
 17. Thelinear incendiary strand of claim 16, wherein the fuel component layerof the tape is in a discontinuous pattern on both upper and lowersurfaces of the pyrotechnic element in order to form a centrallongitudinal gas channel in connective arrangement with multiple lateralgas channels.
 18. The linear incendiary strand of claim 17, wherein thelateral gas channels are open to the exterior lateral edges of the tapeand are longitudinally offset to either side of the longitudinal gaschannel.
 19. The linear incendiary strand of claim 1, further comprisinga longitudinal gas channel.
 20. The linear incendiary strand of claim19, wherein the interior surface of the gas channel comprises the fuelcomponent.
 21. The linear incendiary strand of claim 19, wherein the gaschannel is covered by an exterior sheath.
 22. The linear incendiarystrand of claim 21, wherein the exterior sheath is selected from thegroup consisting of paper, plastic film, or coated fabric compositions.23. The linear incendiary strand of claim 13, wherein the pyrotechnicelement comprises an extruded strand formed from a mixture of anoxidizing agent, a fuel compound and a binder.
 24. The linear incendiarystrand of claim 23, wherein the binder is selected from the groupconsisting of cellulose nitrate, cellulose acetate, polyacrylate,poly-isoprene, poly-butadiene, polyethylene and polypropylene.
 25. Thelinear incendiary strand of claim 23, wherein the binder is celluloseacetate butyrate.
 26. The linear incendiary strand of claim 13, whereinthe pyrotechnic element comprises a cellulose fiber substrate that isimpregnated and coated with a pyrotechnic composition comprised ofoxidizer and fuel compounds.
 27. The linear incendiary strand of claim26, wherein the cellulose fiber substrate is paper.
 28. The linearincendiary strand of claim 26, wherein the cellulose fiber substrate isa loose woven cotton textile fabric.
 29. The linear incendiary strand ofclaim 26, wherein the pyrotechnic composition comprises ammoniumperchlorate, potassium perchlorate, powdered aluminum, 325 mesh, andbinder.
 30. The linear incendiary strand of claim 13, further comprisinga longitudinal gas channel, wherein the interior surface of the gaschannel comprises the fuel component, wherein the pyrotechnic elementcomprises a fabric substrate with a coating of pyrotechnic compositionpositioned centrally within the gas channel, and wherein the lateraledges of the pyrotechnic element are fixedly embedded in the fuelcomponent along the longitudinal axis of the incendiary strand.
 31. Thelinear incendiary strand of claim 30, further comprising a plurality ofvent passages that are radially disposed about the circumference of thestrand and that are arranged at equidistance intervals along the strand.32. The linear incendiary strand of claim 1, wherein the reinforcingmeans comprises an exterior sheath.
 33. The linear incendiary strand ofclaim 1, wherein the reinforcing means comprises a continuous textilesubstrate.
 34. The linear incendiary strand of claim 1, wherein thereinforcing means comprises elongate fiber particles in a structuralcomposite matrix.
 35. The linear incendiary strand of claim 1, furthercomprising means for fragmenting the strand subsequent to ignition. 36.The linear incendiary strand of claim 35, wherein the means forfragmenting the strand subsequent to ignition comprises rapidly burninglongitudinal reinforcing elements placed at selective intervals alongthe strand.
 37. The linear incendiary strand of claim 35, wherein themeans for fragmenting the strand subsequent to ignition comprises ventpassages that cause the strand to melt and separate into individuallyburning pieces.
 38. The linear incendiary strand of claim 1, wherein thestrand is in the form of a tape.
 39. The linear incendiary strand ofclaim 1, wherein the strand is in the form of a ribbon.
 40. The linearincendiary strand of claim 1, wherein the strand is in the form of acord.
 41. The linear incendiary strand of claim 1, wherein the strand isin the form of a tube.
 42. The linear incendiary strand of claim 1,wherein the strand is in the form of a filament.
 43. The linearincendiary strand of claim 1, wherein the strand can be wound upon aspool of suitable diameter for handheld deployment.
 44. The linearincendiary strand of claim 1, further comprising weatherproofing means.45. The linear incendiary strand of claim 44, wherein theweatherproofing means comprises water-resistant coatings.
 46. Theincendiary strand of claim 44, wherein the weatherproofing meanscomprises water-resistant compositions.
 47. A method of ignitingvegetative matter over an area of land using the linear incendiarystrand of claim 1, comprising the steps of: laying out one or morelinear incendiary strand(s) in a predetermined pattern throughout thearea to be burned; and igniting each incendiary strand in succession atintervals of time selected to achieve the desired fire behaviorcharacteristics.
 48. A method of setting backfires in wildfire controlactivities using the linear incendiary strand of claim 1, comprising thesteps of: placing a first linear incendiary strand among combustiblevegetative matter adjacent to fire control lines in the path of anadvancing wildfire; and igniting the first linear incendiary strandeither by direct application of flame or by electrical activation. 49.The method of claim 48, further comprising the steps of: placingadditional linear incendiary strands along strips parallel inorientation to the first linear incendiary strand, at a distance ofspacing between strips that is determined according to fuel, weather andtopographical conditions; and igniting the additional incendiary strandsin a sequence timed to result in a line of fire being drawn from thecontrol line outwardly toward the advancing wildfire and against thedirection of the prevailing winds.
 50. The method of claim 49, furthercomprising igniting the incendiary strands precisely at the onset ofindraft winds generated from the advancing wildfire.
 51. A method ofproducing the pyrotechnical element of the linear incendiary strand ofclaim 30, wherein the pyrotechnical element is produced by: soaking thefabric substrate in a saturated aqueous solution of a water-solubleoxidizing agent; squeezing the fabric to remove excess solution; dryingthe fabric in a warm air drying tunnel; coating the fabric with arapidly burning pyrotechnic composition; drying the fabric; and cuttingthe fabric into strips.
 52. The method of claim 51, wherein the fabricsubstrate is bleached cotton cheesecloth.
 53. The method of claim 51,wherein the rapidly burning pyrotechnic composition comprises ammoniumperchlorate, potassium perchlorate, powdered aluminum, 325 mesh, and abinder.
 54. The method of claim 53, wherein the binder is prepared bydissolving nitrocellulose solids in acetone in increments until thesolution is viscous and heavy-bodied.
 55. A method of manufacturing thelinear incendiary strand of claim 12, comprising the following steps:heating a combustible thermoplastic resin to a temperature of 200degrees C.; soaking cedar sawdust fibers in a saturated aqueous solutionof a water-soluble oxidizing agent; drying the cedar sawdust fibers;adding the cedar sawdust fibers to the hot thermoplastic resin inincrements at a temperature of about 150 degrees C. until thethermoplastic resin has a thick, dough-like consistency; forming thethermoplastic resin into the shape of a hollow strand with thepyrotechnic element embedded within a portion of its interior wallsusing a cross-head extrusion technique; cooling the strand; andperforating or drilling vent passages into the strand.
 56. The method ofclaim 55, further comprising the step of applying a weatherproofinglayer to the outside of the hollow strand by passing it quickly throughan immersion bath of a melted thermoplastic polymer and rapidly coolingit in a coolant bath.
 57. The method of claim 56, wherein the meltedthermoplastic polymer is plasticized cellulose acetate butyrate.
 58. Themethod of claim 55, further comprising the step of applying aweatherproofing layer to the outside of the hollow strand by spiralwrapping an adhesive-backed cellulose acetate film around the strand'souter surface.
 59. The method of claim 55, wherein the combustiblethermoplastic resin comprises pine resin derivative, cellulose acetatebutyrate, and a plasticizing agent.
 60. The method of claim 59, whereinthe plasticizing agent is selected from the group consisting of glyceryltriacetate, butyl ricinoleate and triethyl citrate.
 61. The method ofclaims 51 or 55, wherein the water-soluble oxidizing agent is ammoniumperchlorate.
 62. The method of claims 51 or 55, wherein thewater-soluble oxidizing agent is potassium nitrate.
 63. A method ofmanufacturing the linear incendiary strand of claim 1, comprising thesteps of: heating a combustible thermoplastic resin to form the fuelcomponent; and laminating an upper covering layer and a lower coveringlayer together with a fuel component layer and a pyrotechnic element toform a tape, wherein the fuel component layer is in a discontinuouspattern on both upper and lower surfaces of the pyrotechnic element inorder to form a central longitudinal gas channel in connectivearrangement with multiple lateral gas channels, and wherein the lateralgas channels are open to the exterior lateral edges of the tape and arelongitudinally offset to either side of the longitudinal gas channel.64. The method of claim 63, wherein the pyrotechnic element is producedin the same manner as set forth in claim
 51. 65. The method of claim 63,wherein lamination of the upper covering layer, lower covering layer,fuel component layer and pyrotechnic element comprises the followingsteps: mounting spools of upper covering layer and lower covering layeron separate feed spindles of a roll laminating apparatus; mounting aspool of pyrotechnic element on a feed spindle between the spools ofupper and lower covering layers; drawing the pyrotechnic element througha double-sided slot-die extrusion apparatus comprising two separate slotdie extrusion heads on each side of the pyrotechnic element; arrangingthe extrusion heads to apply two separated strips of heatedthermoplastic fuel component to each side of the pyrotechnic element toa thickness of about 20 mils per side; modulating the flow from eachextrusion head by linear indexing means to provide discontinuous stripslongitudinally; and drawing the upper and lower covering layers togetherwith the coated pyrotechnic element and feeding the layers throughsuitably spaced pressure rollers to form a permanent lamination.
 66. Themethod of claim 65, wherein the total thickness of the laminated layersis about 60 mils.
 67. The method of claim 65, wherein the upper andlower covering layers are made of polymeric film.
 68. The method ofclaim 65, wherein the upper and lower covering layers are made of coatedfabric.
 69. The method of claim 65, wherein the upper and lower coveringlayers are made of paper.
 70. The method of claim 65, wherein the upperand lower covering layers are made of creped kraft paper impregnatedwith an oxidizing agent.
 71. The method of claim 70, wherein the crepedkraft paper is impregnated with an oxidizing agent by: soaking the paperin a saturated aqueous solution of an oxidizing agent; and drying thepaper.
 72. The method of claim 71, wherein the creped kraft paper issoaked in the oxidizing agent solution at the same time that it issubject to the wet creping process used to produce the creped paper. 73.The method of claim 70, wherein the creped kraft paper is furtherimpregnated and coated with a waterproofing agent.
 74. The method ofclaim 73, wherein the waterproofing agent is a cellulose acetatebutyrate lacquer.
 75. The method of claim 73, wherein the waterproofingagent is a non-petroleum-based microcrystalline wax solution.